Magica et Machina

Shoud you avoid magic because it provides a Deus Ex Machina?

Deus Ex Machina (hard c, just because Latin is a dead language doesn't mean you can butcher the pronunciation) originated in Greek theatre. If a play ended up long, or the writer couldn't conclude the plot (or anything else required that the play end quickly) an actor would decend (via crane) playing the part of the gods and sort out the loose ends (the series had not been invented yet). Forces of nature are certainly useable in a similar manner (H.G. Wells's War of the Worlds ended that way, one of the few paletable uses of the technique).

Many of the great Greek poets we remember today condemmed the practice, and were probably right to do so. First and formost, it's a perfect example of poor writing. Rather than creating a coherant plot, the author chops off the resolution. Rather than revising, he places an omnipotent character in the play to fill plot holes, erase mistakes and perform the job of the editor. Also, one purpose of writing is to provide a look into life and the world, and a Deus Ex Machina throws out the human element.

Back on topic, some people suggest that you should use technology in place of magic. While magic is a construct of pure imagination, technology is something concrete and scientific, right? Well...the author makes up whatever rules of magic are needed for the story, and whatever science is needed can be made up as well; how many Star Trek episodes end with the engineer/science office inventing some nonsense? Technology is no different from magic, we've just given it a chrome faceplate and LEDs.

There is nothing wrong with using magic, provided it's limited well short of the deus-ex-machina level. You can limit scope: Tolkien (and Terry Brooks for that matter) restrict magic to a handful of people. Or have powerful tradeoffs and weaknesses (how many times has the magician spent years wasting away to learn his trade). Reduce the number of situations it can be used for (the basis of most RPG games). Or even make magic so ubiquitous that it makes no difference.

Consider it from another direction: could you tell the same story without anything beyond current technology? Lord of the Rings as a spy thriller? Honor Harrington with the British Navy? Magic and Technology are there to magnify the characters and story. Open up a larger world for the backdrop, eliminate delays in the plot, dismiss minor points without needless clarification, all perfectly legitment uses, which do not disturb the story.